North Korea executed at least 17 of its citizens in 2013 and six in the first half of this year, mostly for political motives and nonviolent crimes, a civic group said Monday, pointing to rampant breaches of human rights in the communist country.

In an annual report on the death penalty, the Brussels-based rights group Hands Off Cain said at least 4,106 executions took place in 22 countries last year.

Topping the list is China with at least 3,000, followed by Iran with 687, Iraq with 172, Saudi Arabia with 78 and the U.S. with 39.

In North Korea, the killings were carried out by firing squad and chiefly targeted political prisoners such as Jang Song-thaek, the purged uncle of leader Kim Jong-un, and his confidants, it said.

North Korea carried out 20 executions in 2012, the group said.

But the organization indicated that the real figures could be much higher in such countries as North Korea, Egypt, Malaysia and Syria, where “absolute secrecy” is enforced by authorities and news of executions does not filter through to the local media.

“Many of these countries do not issue official statistics on the practice of the death penalty, therefore the number of executions may, in fact, be much higher,” it said.

The latest data on North Korea is in line with a survey released in February by the U.N. Commission of Inquiry, which detailed “systematic, widespread and gross” human rights violations in the oppressive country that constitute crimes against humanity. It called for the offenders including leader Kim Jong-un to be brought to an international criminal justice mechanism.

The landmark report estimated that between 80,000 and 120,000 political prisoners are locked in sprawling gulags across the country, based on satellite imagery and testimony from survivors, former guards and other witnesses.

“The unspeakable atrocities that are being committed against inmates of the kwanliso political prison camps resemble the horrors of camps that totalitarian states established during the 20th century,” the report reads.

“The institutions and officials involved are not held accountable. Impunity reigns.”

As a follow-up measure, the Office of the High Commissioner for Human Rights plans to launch a field office in South Korea to monitor and study the situation across the border.

The office is expected to open in the autumn in Songdo, a business district of Incheon that houses various U.N. agencies, with about five officials from the headquarters and local staff, according to Seoul officials.